This application claims the priority of German application 198 28 065.3, filed Jun. 24, 1998, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a honeycomb structure seal between a rotating element and a stator element of a turbine, particularly for a gas turbine, having a brush-against section facing the tips of the turbine blades as well as having a base plate facing the other element of the turbine. In particular, the above-mentioned turbine blades may be rotor blades so that the base plate faces the casing wall (=stator element) of the turbine. However, as an alternative, the base plate may also face the rotating turbine shaft so that the above-mentioned brush-against section faces the tips of the turbine stator blades. With respect to the technical environment, reference is made to German Patent Document DE 32 35 745 A1, as an example. In addition, it is explicitly pointed out that the term of the "honeycomb structure" is to be understood in a general sense; that is, it must not necessarily be the honeycomb structure associated with bees familiar to the person skilled in the art. On the contrary, it may be any arrangement of mutually adjacent hollow spaces of any geometry.
Brush-against seals for the rotor blades, for example, of gas turbines, which are arranged on the interior wall of the turbine casing, are, among other designs, also constructed as honeycomb seals. In this case, the honeycomb structure is carried by a base plate, while the web-type walls forming the honeycomb structure face the tips of the rotor blades by means of their free end sections. The honeycomb cells bounded by the web-type walls can be filled at least partially with a suitable insulation material, as described in the above-mentioned document.
Brush-against seals of gas turbines must fulfill two main tasks; specifically, (i) keeping the working gas as effectively as possible from flowing around the rotor blade tips, and (ii) furthermore insulating the turbine case at least in sections with respect to the hot working gas. This thermal insulation effect is to be such that the thermal casing expansion takes place simultaneously with the thermal and the superimposed centrifugal-force-induced expansion of the rotor disk and of the rotor blades in order to minimize the gap measurement between the blade tips and the turbine casing also during transient operating conditions (for example, during the warm-up phase) of the turbine. A minimizing of the gap measurement over the whole working cycle of a gas turbine, particularly of a flight gas turbine, is necessary because any enlargement of the gap measurement causes a reduction of the degree of thrust and efficiency.
These above-described requirements are at least partially met only insufficiently by means of the existing solutions of honeycomb structure seals. Either well-sealing fine-structured honeycomb structures cannot be filled sufficiently well with insulating material, or the coarser, easily fillable honeycomb structures do not have satisfactory sealing properties. As a result, the thermal insulation of the turbine casing is not sufficiently effective. Furthermore, combinations of metal and ceramics (if the honeycomb structure is conventionally metallic and the insulating material filled into the honeycombs is ceramic), particularly in the case of a thermocyclic stress, have a limited service life. Also, the ceramic fillers may cause damage to the inlet webs known to the person skilled in the art.
It is an object of the present invention to provide a remedial measure with respect to the above-described problems.
This object is achieved according to the invention by a multi-layered construction of the honeycomb structure seal such that the base plate is adjoined by an air-evacuated honeycomb structure section which is therefore insulating in partial areas by a vacuum and which is covered by an intermediate plate, on whose side facing away from the honeycomb structure section the brush-against section is arranged. Further developments and advantages of preferred embodiments are set forth below and in the claims. It should be pointed out again that the so-called honeycomb structure section is to be understood as an arrangement of several hollow spaces of essentially any shape side-by-side.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.